ABSTRACT
Astronauts have complained about poor sleep, sleep loss, and fatigue during their missions. They have shifted sleep and work schedules and there is environmental noise from round-the-clock radio transmissions. Astronauts' brain recordings show they did sleep, and pilot Frank Borman had a 23.7 hour pattern when he lived on a 23.5 hour day on the Gemini VII mission. Yawning has been attributed to boredom, lack of oxygen, social contagion. In mammals yawning may be associated with transitions between periods of high and low activity or arousal. Circadian, circannual, and lunar-tidal rhythms have evolved because of the daily and annual fluctuations in the lighting and environment on earth due to its rotation rate, orbiting rate, and its relationship to the sun and the moon. Insomnia is a word used for sleep difficulty sleeping, or disturbed sleep patterns. Insomnia has been subdivided into five types: broken sleep, falling asleep too late, falling asleep too early, disorganized sleep-wake schedules, and non-24-hour rhythms.
